4-month résumé gap, advice?

I took time out to care for a family member after working as a call-centre agent. It has been a long 3 weeks. I am not sure how much to explain. How did you handle it on your résumé?

Keep everything in writing and save the confirmation numbers. It saved me later.

I listed the volunteering and course under the same dates and kept the explanation to a sentence in the cover letter.